more tests and docs

Author: TomPallister

docs/features/headerstransformation.rst

@@ -85,6 +85,7 @@ Ocelot allows placeholders that can be used in header transformation.
 {BaseUrl} - This will use Ocelot's base url e.g. http://localhost:5000 as its value.
 {DownstreamBaseUrl} - This will use the downstream services base url e.g. http://localhost:5000 as its value. This only works for DownstreamHeaderTransform at the moment.
 {TraceId} - This will use the Butterfly APM Trace Id. This only works for DownstreamHeaderTransform at the moment.
+{UpstreamHost} - This will look for the incoming Host header.
 
 Handling 302 Redirects
 ^^^^^^^^^^^^^^^^^^^^^^

src/Ocelot/Infrastructure/Placeholders.cs

@@ -32,7 +32,7 @@ public Placeholders(IBaseUrlFinder finder, IRequestScopedDataRepository repo, IH
 
             _requestPlaceholders = new Dictionary<string, Func<DownstreamRequest, string>>
             {
-                { "{DownstreamBaseUrl}", GetDownstreamBaseUrl() }
+                { "{DownstreamBaseUrl}", GetDownstreamBaseUrl() },
             };
         }
 
@@ -143,10 +143,8 @@ private Func<Response<string>> GetUpstreamHost()
                     {
                         return new OkResponse<string>(upstreamHost.First());
                     }
-                    else
-                    {
-                        return new ErrorResponse<string>(new CouldNotFindPlaceholderError("{UpstreamHost}"));
-                    }
+
+                    return new ErrorResponse<string>(new CouldNotFindPlaceholderError("{UpstreamHost}"));
                 }
                 catch
                 {

test/Ocelot.UnitTests/Infrastructure/PlaceholdersTests.cs

@@ -134,5 +134,22 @@ public void should_return_upstreamHost()
             var result = _placeholders.Get("{UpstreamHost}");
             result.Data.ShouldBe(upstreamHost);
         }
+
+        [Fact]
+        public void should_return_error_when_finding_upstbecause_Host_not_set()
+        {
+            var httpContext = new DefaultHttpContext();
+            _accessor.Setup(x => x.HttpContext).Returns(httpContext);
+            var result = _placeholders.Get("{UpstreamHost}");
+            result.IsError.ShouldBeTrue();
+        }
+
+        [Fact]
+        public void should_return_error_when_finding_upstream_host_because_exception_thrown()
+        {
+            _accessor.Setup(x => x.HttpContext).Throws(new Exception());
+            var result = _placeholders.Get("{UpstreamHost}");
+            result.IsError.ShouldBeTrue();
+        }
     }
 }